1. Technical Field of the Invention
The present invention relates to a telecommunications network and, in particular, to the rerouting of incoming calls to a ported telecommunications terminal within a telecommunications network.
2. Description of Related Art
Each telecommunications terminal associated with a particular telecommunications network is assigned a unique identification number for receiving an incoming call. Within the Global System for Mobile (GSM) communications or the Personal Communications System (PCS), each mobile station is assigned a unique identification number known as a Mobile Station Integrated Services Digital Network (MSISDN) number. Similarly, each wireline telecommunications terminal connected to a particular Public Switched Telephone Network (PSTN) is assigned a unique directory number. Such an MSISDN or directory number is dialed whenever a caller wants to communicate with a particular telecommunications terminal. The telecommunications network determines, by analyzing a part of the dialed number, the home PSTN or Public Land Mobile Network (PLMN) associated with the called party terminal and accordingly routes the call to the destination telecommunications node serving the called party terminal.
Telecommunications subscribers often relocate from a first service area served by a first telecommunications service provider to a second service area served by a second telecommunications service provider as they relocate from one city to another or one geographic area to another. By relocating, a particular subscriber's pre-existing subscriber agreement with the first telecommunications service provider is terminated and a new subscription agreement with the second telecommunications service provider must be established. However, a specific series of MSISDN or directory numbers are pre-assigned to each telecommunications service provider, or more particularly, each telecommunications node (e.g., local exchange or home location register) within an associated PLMN or PSTN. Therefore, by relocating from one telecommunications network to another, the telecommunications subscriber or associated terminal accordingly must be assigned a new MSISDN or directory number within the series pre-assigned to the new second telecommunications service provider. Changing the assigned MSISDN or directory number is a cumbersome process in part because the telecommunications user must inconveniently notify all relevant parties of his new MSISDN or directory number.
American Telephone & Telegraph (AT&T) has proposed the concept of the use of a location routing number (LRN) to alleviate some of the analogous problems associated with wireline terminals of subscribers who move from one region or network to another without changing their directory numbers. In accordance with the LRN concept, a centralized database storing a network address representing the end office currently serving the wireline terminal is queried by a tandem switch or a service switching point (SSP) within a Public Switched Telephone Network (PSTN) to route an incoming call to the correct end office.
A U.S. application for patent Ser. No. 08/656,723, entitled "Routing An Incoming Call To A Ported Mobile Station Within A Telecommunications Network", filed by Gun-Shin Chien on Jun. 3, 1996 (hereinafter referred to as the Chien application), now U.S. Pat. No. 5,839,072, which is hereby incorporated by reference herein, further discloses a system and method for maintaining a centralized database for storing data correlating a particular MSISDN with a network address representing the home Public Land Mobile Network (PLMN) and, more particularly, the home location register (HLR) within that particular PLMN currently serving the ported mobile station rather than the HLR or PLMN to which that number was originally assigned. Accordingly, when the centralized database is queried, the network address representing the current HLR serving the ported mobile station is returned.
Even though the Chien application and the LRN concept enable the routing of an incoming call to a ported telecommunications terminal (e.g., wireline terminal and mobile station) within a telecommunications network, there are certain system characteristics which are not optimal for certain applications.
The telecommunications network cannot determine whether the called party telecommunications terminal has been ported just by analyzing the received MSISDN or directory number. In instances when only one number within a given series is ported out of a particular PLMN or PSTN, all incoming calls intended for that particular PLMN or PSTN have to be inefficiently queried to the centralized database. As an illustration, out of the 214-555-XXXX series, even if only one number is ported, incoming calls for each and every one of the 214-555-XXXX number series have to be queried to the centralized database.
Such an exhaustive querying mechanism is both inefficient and wasteful. Accordingly, there is a need for a mechanism to reduce the number of queries performed to the centralized database to reroute incoming signals to the current PLMN or PSTN serving a ported telecommunications terminal.